The skin crawls, the stomach turns: ectoparasites and pathogens elicit distinct defensive responses in humans

Tom R. Kupfer, Daniel M.T. Fessler, Bozhi Wu, Tiffany Hwang, Adam Maxwell Sparks, Sonia Alas, Theodore Samore, Vedika Lal, Tanvi P. Sakhamuru, Colin Holbrook

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Disgust has long been viewed as a primary motivator of defensive responses to threats posed by both microscopic pathogens and macroscopic ectoparasites. Although disgust can defend effectively against pathogens encountered through ingestion or incidental contact, it offers limited protection against ectoparasites, which actively pursue a host and attach to its surface. Humans might, therefore, possess a distinct ectoparasite defence system-including cutaneous sensory mechanisms and grooming behaviours-functionally suited to guard the body's surface. In two US studies and one in China, participants (N = 1079) viewed a range of ectoparasite- and pathogen-relevant video stimuli and reported their feelings, physiological sensations, and behavioural motivations. Participants reported more surface-guarding responses towards ectoparasite stimuli than towards pathogen stimuli, and more ingestion/contamination-reduction responses towards pathogen stimuli than towards ectoparasite stimuli. Like other species, humans appear to possess evolved psychobehavioural ectoparasite defence mechanisms that are distinct from pathogen defence mechanisms.

Original languageEnglish
Article number20210376
Pages (from-to)1-8
Number of pages8
JournalProceedings of the Royal Society B: Biological Sciences
Issue number1955
Early online date28 Jul 2021
Publication statusPublished - 28 Jul 2021

Bibliographical note

This record is sourced from MEDLINE/PubMed, a database of the U.S. National Library of Medicine


FundersFunder number
Horizon 2020 Framework Programme800096


    • behavioural immune system
    • disgust
    • ectoparasites
    • grooming
    • pathogens


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